I post here after some research and attempts to understand the problem by myself. I followed a tutorial to push on heroku my app developped locally : https://dash.plotly.com/deployment
The application works fine (after a few modifications on the requirements). The unique problem is the fact that the svg pictures on the icons button are not loaded, the url is not found. Basically it is coded in the app as :
html.Button(children=[html.Img(src=app.get_asset_url('Seldes_fit.svg'),style={'width':'100%'})
I found some topics about Django static assets system, but I don't have any information on how to proceed to provide correct paths to the assets to heroku. If anyone is having those informations, it would be wonderful for beginners like me.
Many thanks in advance! :)